Activist teachers are increasingly organizing within and beyond their unions to respond to political trends toward austerity and the privatization of public education (Hursh, 2004; Quinn & Carl, 2015; Ravitch, 2010, 2013). Teacher-led grassroots groups often strive to partner in meaningful ways with parents and communities (Weiner, 2012), but simultaneously overlook how deeply embedded community histories shape the community and policy context (Crenshaw, 2011; Delgado & Stefancic, 2012; Gadsden, 1994), and teachers’ organizing and professional practices (Maton, 2016). The enhanced recent visibility of race-inflected social activism (#BlackLivesMatter, 2016) raises significant questions about how politically active teachers understand and engage with issues of racial justice. This dissertation asks: When politically active teachers come together in an inquiry group to discuss structural racism, how do they engage in individual and collective learning processes? And, how do they perceive the shape, form and effect of their learning? Methodologically, the study draws from participatory (Cochran-Smith & Lytle, 2009; McIntyre, 2008) and race feminist (Delgado-Bernal, 1998; Smith, 1987) qualitative research traditions. The study examines the work of an inquiry group composed of nine racially and gender diverse participant who are active members of a change-seeking union caucus. Data sources include inquiry group meetings, interviews, field notes and written texts. The dissertation builds a new theory for understanding the nature, form and function of teachers’ collaborative learning about racial justice. This study defines collaborative learning as the collective and social search for knowledge and transformation, and shows that it is composed of four interconnected and mutually reliant components: learning, pedagogy, relationships, and diffusion. Furthermore, the study finds that inquiry-based collaboration among politically active teachers, on projects where the goal is to build a common mission, vision and project, and where there is diversity in race, gender and a range of experiences with prejudice and discrimination, holds great potential for triggering teacher learning and addressing social justice issues within and beyond activist organizations and schools.